首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1522128篇
  免费   26195篇
  国内免费   7005篇
电工技术   34503篇
综合类   6385篇
化学工业   272402篇
金属工艺   64765篇
机械仪表   43378篇
建筑科学   46229篇
矿业工程   11499篇
能源动力   50442篇
轻工业   111951篇
水利工程   15500篇
石油天然气   37877篇
武器工业   132篇
无线电   197645篇
一般工业技术   287230篇
冶金工业   170959篇
原子能技术   34198篇
自动化技术   170233篇
  2021年   15653篇
  2020年   11919篇
  2019年   14699篇
  2018年   16953篇
  2017年   16427篇
  2016年   21931篇
  2015年   17495篇
  2014年   28778篇
  2013年   88002篇
  2012年   35963篇
  2011年   49161篇
  2010年   43467篇
  2009年   51810篇
  2008年   45421篇
  2007年   42838篇
  2006年   44669篇
  2005年   39821篇
  2004年   41756篇
  2003年   41697篇
  2002年   40524篇
  2001年   37433篇
  2000年   35842篇
  1999年   35180篇
  1998年   48085篇
  1997年   40761篇
  1996年   36260篇
  1995年   31185篇
  1994年   29167篇
  1993年   29087篇
  1992年   26164篇
  1991年   23273篇
  1990年   23652篇
  1989年   22704篇
  1988年   21213篇
  1987年   19485篇
  1986年   18843篇
  1985年   22163篇
  1984年   22334篇
  1983年   20246篇
  1982年   19237篇
  1981年   19379篇
  1980年   17957篇
  1979年   18443篇
  1978年   17707篇
  1977年   17465篇
  1976年   18385篇
  1975年   15975篇
  1974年   15464篇
  1973年   15574篇
  1972年   12991篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
2.
3.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
4.
5.

Romanian policy makers have to perceive that human intervention on river basins land cover is influencing rainfall-runoff relation and the used methodology cannot accurately estimate watershed surface flow transformations. Global water cycles and energy fluxes understanding is leading to better predictions of land atmosphere interaction and local hydro-climates evolution. The water transfer time determination from rainfall to runoff needs accurate measurements of river basins hydrological parameters. Here, we analyzed and compared the lag time value results of two different methodologies (curve number and rational methodology) used for 54 Romanian small catchment areas study. The focus of this paper is the lag time evaluation and interpretation for an effective implementation of the best methodology approach in the Romanian geographical space. Our research in small river basins was developed using remote sensing technology maps, GIS and environmental datasets in combination with field work on every drainage basin in order to assess the specific morphological features and validate the land cover typology. We found that Soil Conservation Service - Curve Number (SCS-CN) method is widely used according to USA landscape features classification, but not necessarily applicable to Romanian river basins characteristics. Our results show how the official Romanian rational methodology national standard (RNS) can be improved and the limits of SCS-CN method.

  相似文献   
6.
7.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
8.
9.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号